KR20010043027A - Method for reducing metal oxides and device for implementing said method - Google Patents

Abstract

A method for the reduction of metallic oxides and a rotating-hearth furnace. The method is for the reduction of metallic oxides in a furnace with a ring-shaped rotating hearth in which a carbonaceous reducing agent and metallic oxides are deposited in a strip on a part of the rotating hearth and are then transported in a roughly helical movement to a discharge device. The reducing agent is preheated and mixed with the preheated metallic oxides before and/or during their deposition on the rotating hearth. In a first reducing stage, the volatile components of the carbonaceous reducing agent (mainly methane and hydrogen) are used to initiate the reduction of the metallic oxides and, in a second reducing stage, carbon monoxide is used. The rotating-hearth furnace is subdivided into a charging zone, at least one intermediate zone adjacent to the charging zone, and a discharge zone adjacent to the intermediate zone.

Description

Metal oxide reduction method and apparatus for implementing the said method TECHNICAL FIELD

Direct reduction of metal oxides, especially ores, as well as various iron oxides to be regenerated, has developed in recent years.

Luxembourg patent LU-60981-A (Societe Anonyme des Minerais) describes a method for producing sponge iron using a continuous rotating-hearth reactor, moving the material from side to center. Is fed only coal, the coal is coked, and then iron ore in the form of pellets or in a pulverized form and preheated to the reaction temperature. At this time, coal can be moved toward the center of the melting furnace by fixed scrapers, and coke-treated coal and ore are mixed when the rotary hearth rotates. After the reaction has taken place, the charge is discharged through the central shaft.

One disadvantage of the prior art is that the volatile components of the coal do not participate in the reduction of metal oxides. By this method, it becomes impossible to obtain high productivity and high uniformity with respect to the temperature and the material of the charge.

The present invention relates to a method for reducing a metal oxide, in particular iron oxide, and an apparatus for carrying out the method.

1 is a plan view of a rotary melting furnace in which a stirring bar is distributed therein.

2 is a front sectional view of a rotary melting furnace.

3 shows a furrow formed during charging.

4 shows a furrow of a charge formed by a first action of a blade located on a fixed stir bar.

5 shows a furrow of a charge formed by a second operation of a blade located on a fixed stir bar.

6 is a front sectional view of a blade having a stirring rod and an arm for fixing the stirring rod.

An object of the present invention is to provide a metal oxide reduction method that more effectively utilizes the reducing ability of the volatile component of the carbonaceous reducing agent.

According to the invention, this object is achieved by a melting furnace metal oxide reduction process in an annular rotary hearth. Here the carbonaceous reducing agent and the metal oxide in the annular rotary hearth are introduced into the strip on a portion of the rotary hearth and are moved to the discharge device in a substantially helical operation. A feature of the process is that the reducing agent is preheated and mixed with the preheated metal oxide during or before being introduced to the rotary hearth, and in the first reduction step a carbonaceous reducing agent (mostly methane and hydrogen). The volatile component of is used to cause the reduction of the metal oxide, and carbon monoxide is used in the second reduction step.

Unlike the process of the prior art, the process according to the invention uses a portion of the volatile components of the carbonaceous reducing agent, in particular methane and hydrogen, for reducing capacity.

By the method according to the present invention, it is possible to increase the reaction rate by mixing the metal oxide and the carbonaceous reducing agent to effectively use the reducing ability of the volatile component of the carbonaceous reducing agent. The volatile components are then forced through a preheated mixture that forms a furnace charge.

One of the advantages of the process lies in the fact that a volatile component, i.e., the evaporating gas from the carbonaceous reducing agent, is used in the first step to reduce the metal oxide. On the other hand, as is well known, the gas is burned and used to heat solid materials.

The metal oxide is thus reduced in two steps or by at least two different chemical reactions. The reaction steps occur simultaneously or sequentially.

The first reduction step is carried out by using hydrogen and / or methane released while the carbonaceous reducing agent is heated. The reaction process of the reaction is more preferable than the reaction process of carbon monoxide at 900 ℃ or less. The volatile components mentioned above are brought into contact with the metal oxides introduced on the hearth which are gradually released and in particular have operating conditions relating to the reaction temperature, thereby participating in the reduction of the oxides.

The metal oxide and released reducing gas are brought into contact at the highest possible temperature without overturning the process of the reduction process. The carbonaceous reducing agent is preferably preheated to 200 ° C while the metal oxide is preferably preheated to 850 ° C.

Both components are preferably preheated by the heat recovered from the combustion gases discharged from the furnace into the heat exchanger.

These operating conditions significantly increase the production capacity per unit area and reduce the amount of carbon dioxide released into the atmosphere per unit amount of the reduced metal oxide obtained.

The method also has the advantage of reducing dust emissions outside the furnace by controlling the velocity of the gases while keeping the volume of the furnace at a minimum. The obtained large amount of spongy iron has better homogeneity than the product obtained by the prior art in reduction degree.

It is preferred that the carbonaceous reducing agent is exceeded by at least 10%. This has been defined in relation to the theoretical amounts for the reduction of oxides.

According to a particular embodiment, a method for the direct reduction of metal oxides in a rotary-bed furnace has been proposed. In this rotary-furnace smelter, a multi-layered charge is placed on a portion called the furnace charge zone for a certain ring width. The ring width here is influenced by the diameter and capacity of the furnace. The layers can be introduced simultaneously or sequentially.

The concentration of the metal oxide and the carbonaceous reducing agent in the input layer may be different. It is preferred that the concentration of the gold oxide in the upper layer is greater than the concentration of the metal oxide in the lower layer. The lower layer thus contains excess carbonaceous reducing agent. As a result, the concentration of carbonaceous reducing agent in the upper layer is smaller than that of the lower layer. In such a case, a kind of increase or decrease is made within the concentration of the metal oxide. That is, the concentration increases from the hearth towards the upper surface of the charge. Thus, larger amounts of volatile components are released in the lower layer, and this gas diffuses through the layer toward the upper surface of the charge. Here, the volatile components collide with a high concentration of metal oxide. Since the temperature of the bottom layer is lower than the temperature of the top layer, the volatile components of the carbonaceous reducing agent are gradually released into the bottom layer and impinge on the very hot metal oxide while spreading towards the top surface. In fact, the top layer is hotter than the bottom layer because first the top layer contains a high concentration of metal oxide preheated to a temperature higher than the carbonaceous reducing agent, and secondly the layer is in contact with the furnace atmosphere. Volatile components thus participate more effectively in metal oxide reduction.

The concentration of the carbonaceous reducing agent in the lower layer is preferably between 30% and 70% by weight, and most preferably between 30% and 60% by weight, between the theoretical concentration for complete reduction of the metal oxide and the concentration of 100% by weight.

The concentration of the carbonaceous reducing agent in the lower layer is preferably 25% or less by weight, most preferably 16% or less by weight.

According to a preferred embodiment, the charge is heated to a temperature of 900 to 1250 ° C. inside the melting furnace, preferably at a temperature of 1050 to 1150 ° C.

It is desirable to use metal oxides at the highest feed temperatures possible while avoiding the coagulation action of the metal oxides.

The mixture of carbonaceous reducing agent and metal oxide, or the charge, is overturned and gradually mixed while staying inside the furnace.

According to another preferred embodiment, the surface of the charge has its shape by forming a furrow or hummock on the surface. This is to facilitate heat exchange between the upper part of the furnace and the charges and is achieved by increasing the radioactivity from the furnace and increasing the surface area for heat exchange with the furnace atmosphere.

The slope of the furrow or protrusion is typically 40 ° to 60 °.

It is preferred that the serrated surface is made on the charge surface.

According to a preferred embodiment, the charge or mixture is charged into the inner part of the annular hearth and moved towards the outer part of the hearth in a substantially helical motion. Next, the reaction takes place and then it is discharged through the outer part of the ring.

The mixture is typically rotated four or more times and then discharged.

The mixture layer or mixture layers of the carbonaceous reducing agent and the metal oxide is preferably introduced on the portion corresponding to 1/4 or less of the ring width.

While staying in the furnace, the volume density of the charges decreases. That is, the volume of the charge is increased. The fluidity of the charges changes, and above all, the stopping angle increases, i.e. the slopes of the protrusions or furrows can increase steeply with the progress of the charge process inside the rotary hearth furnace.

According to a preferred embodiment, the width of the strip changes gradually during the process as the charge is moved from the central part of the rotary hearth toward the outer part. The increase in bulk volume of the charge during the process is mainly compensated by the increase in the slope and strip width of the serrated surface.

Subsequent combustion of the gas released during the reduction is preferably achieved in the inner part of the furnace ring.

Discharge of the gas and movement of the charges in the furnace are advantageously made radially opposite each other.

The reducing agent and the metal oxide are typically preheated by the heat recovered from the combustion gas and subsequent combustion gases.

It has been found advantageous to mix small amounts of lime with metal oxides and / or carbonaceous reducing agents. This is because, firstly, the lime acts as a catalyst for the reaction, and secondly, the lime prevents adhesion to sponges. In addition, lime generally aids in the desulfurization of pig iron and the formation of more fluid slugs or clinkers.

In a particular use, a mixture layer of metal oxides and carbonaceous reducing agents is formed by a pellet layer mixing the components.

The term "metal oxide" refers to metallic ores, in particular iron ores and pellets, if necessary, as well as metal oxides to be formed in the manufacturing process for producing iron and steel using, for example, furnaces, steel plants, electric furnaces or rolling mills. In the form of a mixture of coke powder or coal with an oxide source.

The term "carbonaceous reducing agent" is interpreted as all carbonaceous materials in solid or liquid form, for example coal, lignite and petroleum extracts. In general, the reducing agent is coal with the highest volatile component concentration possible in the process. It is preferable when the concentration of the volatile component is approximately 15%.

According to another feature of the present invention, a rotary hearth furnace for metal oxide reduction is also proposed. The melting furnace

Charging zone;

At least one intermediate zone adjacent the charging zone;

A discharge zone adjacent said intermediate zone;

It includes an annular rotary hearth broken down into. The charging zone here comprises a device for loading the charge on the strip of the rotary hearth. The charge then comprises a single or more metal oxide and reducing agent mixed layer. The intermediate zone, which may also be referred to as the charging zone of the melting furnace, comprises a device for radially feeding the charge as the hearth rotates, while gradually stirring the upper part of the charge with the lower part. The discharge zone here comprises a discharge device for discharging the metallized charge at one or more discharge points.

In a preferred embodiment, the melting furnace comprises an apparatus for forming furrows or protrusions on the surface of the input layer to obtain an essentially serrated surface.

The apparatus for introducing the mixture layer or more mixture layers of the metal oxide and the reducing agent may include an apparatus for mixing the carbonaceous reducing agent and the metal oxide at a high temperature before or after the layer is introduced.

According to a particular embodiment, the discharge device comprises a worm conveyor or deflector. If a deflector is used to carry out the discharge from the melt, the width of the furnace ring should be larger than with a worm conveyor. The reason for this is that, with regard to the high temperature spread inside the furnace, the worm drive is mechanically overloaded beyond a certain length.

The melting furnace advantageously comprises a device for stirring with a stirring rod provided with a blade. In this case, the blades are arranged in a teeth manner of the stirring rods, and the stirring rods are radially fixed in the melting furnace.

The stir bar comprises a blade passing through the bed and simultaneously moving the mixture radially towards the outlet of the ring.

The blades are generally offset, i.e. arranged slightly staggered with respect to the furrows formed by the blades of the preceding stir bar, thereby removing or planarizing one side of each furrow and forming a new furrow.

According to a preferred embodiment, the first operation can flatten the apex of the tooth, which is the hottest part of the furrow, into the concave portion of the furrow, and move one face of each tooth on the front of the adjacent tooth by the second motion. Thereby providing an apparatus for covering the material provided by the first operation.

The working degree of the blade is 20 ° to 30 ° with respect to the furrow tangent. The working degree of the blade can be changed at any time to reverse the direction of radial movement of the charge and to increase the residence time inside the furnace.

The blade was formed to overturn the charge.

The melting furnace advantageously comprises a burner installed on the outer wall of the movable-bed melting furnace and / or on the outer ring of the loop. This is to maintain the melting furnace at a temperature of 1200 ° C to 1550 ° C, preferably 1400 ° C.

The invention is described in more detail by reference to the preferred embodiments of the invention shown in the accompanying drawings.

The principle of operation of the method is shown in FIG. 1.

In FIG. 1 the charging zone is indicated by reference numeral 1 and the discharge area from the rotary hearth 3 is indicated by reference numeral 2, in which the hearth is indicated by an arrow 4 around the axis 5 of the furnace. Rotate counterclockwise as indicated by). The burner fixed to the outer wall of the smelting furnace is indicated by reference numeral 6, and the combustion gas is extracted through the inner wall of the smelting furnace at 7 and delivered to the heat exchanger via 8. Reference numeral 9 denotes a stirring rod supporting the blade, and reference numeral 10 denotes an oxygen injector.

In FIG. 2, the same reference numerals as used in FIG. 1 are used. Reference numeral 11 denotes a charge.

3 shows the furrow 12 before the blister passes.

4 shows a state in which the height of the furrow vertices 13 is leveled before the blades operate.

5 shows a state in which the height of the apex 14 of the furrow is flattened by the second operation of the blade.

FIG. 6 is a schematic cross-sectional view of a vertically perspective view of a stir bar 15 having an outer insulator 16 and an inner water-cooled chamber 17 together with a blade 18 having an arm 19 for fixing to a stir bar. Represented by

Operation of the dual action blade is described in more detail below. At the inlet of the melting furnace is provided an apparatus for forming a furrow with a triangular cross section on the charge surface in order to obtain a serrated surface. In the intermediate section extending the charging zone, the melting furnace comprises an additional dual actuating device. In this case, the dual operation device protects the material of the vertex by planarizing the material forming the vertex of each tooth into an adjacent concave portion by the first operation. The apex material here is rapidly heated and reaches a temperature and / or melting point that becomes agglomerates, making it more difficult to mix with the charges and reduce the metal oxides. The second operation removes one front side of each tooth and, if necessary, moves a portion of the base. The removed material is placed on the front face of the adjacent tooth and covers the material provided by the first operation. As a result, the contents are gradually mixed at increasingly deeper heights and are quickly moved as the roadbed rotates, so that the base of the furrows is rapidly rotated at each of the one or more stages through the entire distance corresponding to the width of each charging region. Is moved on.

In the subsequent second intermediate zone, the melting furnace comprises a similar dual actuating device. The device removes the apex of the tooth by the first operation and flattens this portion to an adjacent concave portion. One front of each tooth is moved to the lower roadbed by the second operation. The moved portion is disposed on the front face of the adjacent tooth and covers the material provided by the first action. The charge is moved radially when the hearth rotates so that it can be rotated several times, preferably four or more times and then discharged toward the ring opposite the charging zone.

Of course, the two zones may have the same device.

Operating conditions in the middle section of the furnace are a compromise between the first conditions of generating the temperature of the charge as quickly and as high as possible, and secondly, the conditions of progressive contact with the top layer or metal oxide layer of the mixture of metal oxides and coal. In this case, since the cooler lower layer is not bonded to the upper end of the lower layer of coal, the temperature of the new mixture thus obtained is at least 600 ° C, in particular about 700 ° C.

The rotational speed of the hearth is 3 to 12 revolutions per hour, preferably 8 revolutions per hour.

Moreover, with regard to the top layer of the charge, it is essentially possible to avoid the charge to be converted to glass, for example by forming a silicate of the fayalite type which has a reducing inhibitory effect. To this end, a means such as a stirring rod ensures rapid mixing of the surface layer with the layer immediately below it.

The objective is to provide a product which, in the production time determined by the lowest point among the charges having a thickness of 5 to 10 cm, generally produces a product in which the metal oxide is reduced according to the degree of change by a prior art reduction method. The aim is to obtain sponge iron with better homogeneity than the produced sponge iron in the shortest possible time.

According to this preferred embodiment, the following is provided. In other words,

The charge is charged for 1/6 to 1/12 of the ring width on the inner side of the ring corresponding to the small circle;

A charge that has been fully rotated four or more times in accordance with the charging conditions for the annulus width is rotated at least 100 times by a stirring rod provided with a blade having a different shape and function according to the region of the melting furnace as described above;

In each blade, the charge is moved radially outward to exhibit approximately helical motion;

Discharging the charge out of the ring by one or two deflectors each having a width corresponding to the width of the charge or a half of the width;

Burners are arranged on the wall on the side of the ring, mainly on the outer wall of the ring, which corresponds to a large circle, and / or on the outer wall of the roof, and the gas in the direction of moving material through the wall on the inner side of the ring, which corresponds to a small circle It is discharged by flowing in opposite directions.

Dual-acting blades of different sizes and shapes allow the blades of the first intermediate zone to gradually agitate the charge to an increasingly lower height to the hearth, while the charge is not yet agglomerated and can still be easily mixed. The blade of the second intermediate zone, which is in a suitable form different from that of the first blade, is placed in the stirring rod in such a manner as to stir the furrow and the base. This can prevent generation of reduced metal oxide sheets that are thick and strong and are difficult to grind and discharge.

The stirring rod is radially arranged in the melting furnace. The first stir bar is located in the first intermediate zone extending the charging zone. The charging zone here is the zone where the material is fed to the furnace.

The blades of the stirring rods are fixedly offset in a slightly staggered form with respect to the furrows formed by the blades of the preceding stirring rods, ie staggered by, for example, 50 mm to remove the inclined surface of each groove or tooth. Mixing (ie, stirring) through the movement of the material in the hearth forms new furrows or teeth. The blade forms a furrow with a triangular cross section over the entire surface of the charge, increasing the surface area of the charge by about 20 to 65% at the interface with the furnace atmosphere, thereby transferring more heat from the furnace to the charge.

The first and second types of dual acting blades are inverted one portion of the charge each time the blade passes through the charge, and initially with metal oxide, then metal oxide and coal, while the lower layer of the charge rises. A mixture of and, finally, a metal oxide that is reduced and is designed to lower the top layer of the charge in contact with the furnace atmosphere.

The ends of the blades are formed by inverting the material so that the top end of the furrow, ie the hottest part, is moved to the newly formed furrow floor to ensure better homogeneity.

If necessary, the end can be cooled, for example, by internal circulation of the coolant.

The stirring rods may be linearly distributed in the other region of the furnace with respect to the passage length in one region of the furnace. This distribution may preferably be nonlinear and will depend on the surface temperature and temperature gradient of the charge.

The amount of carbonaceous reducing agent is determined by the stoichiometric amount necessary to completely reduce the contained metal oxides, reduced by the amount corresponding to the reducing action of the volatile components, and increased by the amount required for dissolution of the sponge iron and subsequent alloying. do.

Through gradual mixing of the lower layer and the metal oxide layer, the temperature is inevitably higher than the layer farther away from the region near the interface of metal oxide and coal:

Greater heat transfer is achieved through an increase in surface area at the interface between the top layer and the furnace atmosphere;

The higher thermal conductivity of the metal oxide layer, which initially exists as a single layer on top of the charge, and then gradually blends, is more efficient than using multiple layers without the need for reducing agents in the case of coal, which hinders the process due to low thermal conductivity. Results in better heat transfer;

Gradual mixing of the layers forming the charge can quickly obtain a uniform temperature throughout the charge;

Metal oxides reach very high temperatures which can make the reactivity more rapid, increasing the efficiency of the reduction process and reducing the working time;

It is gradually released as the temperature rises and the volatile components generated by coal are used efficiently and directly as reducing agents;

The reduction using hydrogen occurs immediately and is optimized so that the reaction process is better than that of CO gas;

Reduction with CO is more effective because the hotter upper layer is not mixed with the lower layer, which is too low in temperature, but gradually with the lower layer with the appropriate temperature;

In principle, it is possible to produce less carbon dioxide per unit mass of reduced metal produced;

Excessively high surface temperature can be avoided so that iron olivine does not occur;

The surface of the charge does not show a reduced metal oxide sheet that is too thick and strong to be difficult to grind and discharge;

Melting furnaces with the desired production purpose will be smaller in volume than other methods using rotary hearth melting furnaces.

The furnace is generally maintained at a dome temperature, preferably 1400 ° C., of 1300 ° C. to 1450 ° C. by means of a burner which is installed on the outer wall of the mobile-furnace melting furnace and which carries out subsequent combustion at the inner side of the ring. .

Continuous mixing of the bottom and top layers means that the maximum surface temperature that can be reached does not exceed 1100 to 1200 ° C.

In addition, the uniformity of the charges can be increased through the methods used here, which significantly increases the thickness of the pellets for faster and more efficient operating cycles, for smaller furnaces, and for optimization of the heat exchanger.

Claims (36)

A method of reducing metal oxides in a melting furnace having an annular rotary hearth in which a carbonaceous reducing agent and a metal oxide are introduced into a strip on a portion of the rotary hearth and then moved to a discharge device in a substantially spiral motion. The reducing agent is preheated and mixed with the preheated metal oxide before or during the loading on the rotary hearth, and in the first reduction step the volatile components of the carbonaceous reducing agent (usually methane and hydrogen) undergo the reduction of the metal oxide. Used to produce carbon monoxide in the second reduction step Metal oxide reduction method. The method of claim 1, The carbonaceous reducing agent is preheated to 200 ° C. and / or the metal oxide is preheated to 850 ° C. The method according to claim 1 or 2, And the carbonaceous reducing agent and / or the metal oxide is preheated by the heat recovered from the combustion gas. The method according to any one of claims 1 to 3, A metal oxide reduction method wherein a charge of a carbonaceous reducing agent and a metal oxide comprising a single mixed layer or more mixed layers is introduced. The method of claim 4, wherein Metal oxide reduction method in which the mixed layer is continuously added. The method of claim 4, wherein Metal oxide reduction method in which the mixed layer is added at the same time. The method according to any one of claims 4 to 6, The mixed layer comprises a different metal oxide and carbonaceous reducing agent concentration. The method of claim 7, wherein The concentration of the carbonaceous reducing agent in the upper layer is preferably 25% or less by weight, in particular 16% or less by weight. The method according to claim 7 or 8, The concentration of the carbonaceous reducing agent in the lower layer is between the theoretical concentration for the complete reduction of the metal oxide and the concentration of 100% by weight, preferably between 30% and 70% by weight and between 30% and 60% by weight Most preferred metal oxide reduction method. The method according to any one of claims 1 to 9, The mixture is heated in a melting furnace to a temperature of 950 ° C to 1250 ° C, preferably 1050 ° C to 1150 ° C. The method according to any one of claims 1 to 10, The metal oxide reduction process used at the highest feed temperature possible without clumping the metal oxide. The method according to any one of claims 1 to 11, And the layer or layers of carbonaceous reducing agent and metal oxide are overturned and gradually mixed while staying in the furnace. The method according to any one of claims 1 to 12, The metal oxide reduction method of the mixture of the metal oxide and the carbonaceous reducing agent has a surface form formed with grooves or projections. The method of claim 13, Metal oxide reduction method of the inclination angle of the furrow or the projection is 20 ° to 65 °. The method of claim 13, The metal oxide reduction method in which the substantially serrated surface is formed on the surface of the mixture of the metal oxide and the carbonaceous reducing agent. The method of claim 14, A method of reducing metal oxides in which the width of the charge strip and the inclination angle of the furrows or protrusions are changed while the charge remains in the furnace. The method according to any one of claims 1 to 16, And the mixture is charged to the inner side of the annular hearth, moved towards the outer side of the hearth in a substantially helical motion, and is reacted and then discharged through the outer side of the ring. The method according to any one of claims 1 to 17, Wherein the mixture is rotated four or more times and then discharged. The method according to any one of claims 1 to 18, A mixture layer or mixture layers of solid reducing agent and metal oxide is introduced onto a portion corresponding to approximately one quarter of the ring width. The method according to any one of claims 1 to 19, And a second combustion of said gas is achieved in the inner portion of the ring. The method according to any one of claims 1 to 20, And the gas discharge and charge movements are radially opposite to each other. The method according to any one of claims 1 to 21, Metal oxide reduction method in which a small amount of lime is mixed with the carbonaceous reducing agent and / or metal oxide. Charging zone; At least one intermediate zone adjacent the charging zone; A discharge zone adjacent said intermediate zone; An annular rotary hearth subdivided into a furnace, the charging zone comprising a device for dosing on a strip of rotary hearth, the charge comprising a single or more metal oxide and reducing agent mixed layer, which may be a charging zone of the melting furnace. The intermediate zone includes a device for radially feeding the charge as the hearth rotates, while gradually stirring the lower portion of the upper portion of the charge, the discharge zone having one metalized charge or Including a discharge device for discharging at a further discharge point Rotary hearth furnace for reducing metal oxides. The method of claim 23, wherein An apparatus for introducing a mixture layer or more mixture layers of a metal oxide and a reducing agent includes a device for mixing a carbonaceous reducing agent and a metal oxide at a high temperature, before or after the layer is introduced or during the introduction. The method of claim 23 or 24, The melting furnace comprising a device for forming a furrow or protrusion on the surface of the charged charge to obtain an essentially serrated surface. The method according to any one of claims 23 to 25, Melting furnace wherein the discharge device comprises a worm conveyor or deflector. The method of claim 25, A melting furnace having a through portion in which the deflector is fixed or adjustable. The method according to any one of claims 23 to 27, Said melting furnace comprising a device for agitating a stirring rod provided with a dual action blade arranged in a teeth manner of said stirring rod, wherein said stirring rod is arranged radially fixed in said melting furnace. The method of claim 28, Melting furnace in which the stirring rod and the blade is cooled. The method of claim 28 or 29, Wherein the stirring rod comprises a blade passing through the bed while moving the mixture towards the discharge side of the ring, or a blade passing through the entire depth of the bed while moving the mixture towards the discharge side of the ring. The method according to any one of claims 28 to 30, The stirring rods are offset, i.e. arranged in a slightly staggered form with respect to the furrows or protrusions formed by the blades of the preceding stirring rods, thereby removing the inclined surface of each furrow to form a new furrow, in which the first operation of the sawtooth A melting furnace covering the material provided by the first operation by flattening the vertex to the concave portion of the furrow and moving one front of each tooth on the front of the adjacent tooth by a second operation. The method according to any one of claims 28 to 31, A smelting furnace in which the blade comprises a work schedule of 20 ° to 30 ° with respect to the tangent to the furrow. 33. The method of claim 32, Melting furnace wherein the workability of the blade can be changed at any time. The method according to any one of claims 23 to 33, wherein A melting furnace, wherein the blades are formed such that the contents are overturned and / or stirred. 35. The method of any of claims 28-34, Melting furnace, the charge rate for the blade is 10cm / s to 50cm / s, preferably 15cm / s to 30cm / s. The method according to any one of claims 23 to 35, The melting furnace comprises a burner provided on the outer wall of the movable hearth melting furnace and / or on the outer ring of the loop for maintaining the melting furnace at a temperature of 1200 ° C. to 1550 ° C., preferably 1400 ° C.